Grouping and Social Behavior of Black-handed Spider Monkeys (Atelesgeoffroyi) at La Suerte Biological Field Station

Results of a short term field study on the grouping patterns of Atelesgeoffroyi at La Suerte Biological Research Station in Costa Rica report how the group size, group composition, and activity budget (specifically feeding, resting, and traveling) of an Ateles troop provide insight into grouping patterns. The troop is estimated at 11 to 15 individuals, with 2 to 3 adult males, 2 to 3 females with infants, at 2 juveniles, and the number of adult females is unknown. No individual animals were recognized in this study. I collected data using instantaneous data collection and focal scan sampling. Solitary individuals were defined as the only individual within view of the recorder; males were observed 82% more than any other solitary individual. Groups with males traveled 22% more than groups without and no subgroup consisted of more than one male, all subgroups with more than three individuals contained one male. Travel frequency had an inverse relationship with group size with groups of two traveling 65% of the time observed and groups of four traveling 24% of the time observed, perhaps because a decrease in individuals is an increase in food for each monkey. My data suggests that males travel more and are more often solitary than other individuals. While solitary, males have an increased opportunity to mate with females from surrounding territories, and increased travel in their territory allows them to chase off intruders who may be interested in either their females or food resources.